Sensor-bearing unmanned underwater vehicles (UUV), as well as cabled ocean observatories, have been deployed extensively to study both natural and man-made phenomena including oceanic processes. Certain types of UUVs are tethered by cable to seafloor observatories or to surface ships. The tethered UUVs have a short range of motion and are limited by the length of the tether. Most wireless communication necessary for un-tethered UUVs is accomplished by acoustic communication systems. Such acoustic communication systems, however, are limited by low band-width and high latency, and do not permit video or other high-rate data transfers. Accordingly, improved underwater optical communication (opticom) systems have been developed such as those described by Fucile et al. in US Patent Publication No. 2005/0232638 and by Farr et al. in U.S. Pat. No. 7,953,326, the latter being incorporated herein by reference.
Opticom uses light instead of sound to carry information. An opticom system encodes a message into an optical signal, and then emits or transmits the optical signal from one communication node through a transmission medium to a receiver at another communication node, which reproduces the message from the received optical signal. The term “communication node” as used herein includes movable opticom systems carried by non-stationary, mobile objects such as a surface ship or a UUV, and non-movable opticom systems at a stationary position such as within an underwater observatory. Advantages of opticom systems are identified for example in a News Release by Woods Hole Oceanographic Institution titled “Optical system promises to revolutionize undersea communications”, published Feb. 23, 2010.
Accordingly, there is a need for an improved communication system that allows high-bandwidth, bidirectional wireless communication among two or more nodes in at least one amorphous medium.